Metal catalysts for selective formation of cyclic carbonates, process for preparing cyclic carbonate using the same and use of cyclic carbonate

ABSTRACT

Provided are a novel metal catalyst for preparing cyclic carbonate, and a method for preparing cyclic carbonate using the same, and more particularly, a method for selectively preparing cyclic carbonate in a high yield and at a higher conversion rate as compared to the existing catalysts, using the metal complex including a ligand represented by Chemical Formula 1 below and a trivalent metal in Group 8 or Group 13 as a catalyst and using various structures of epoxide compounds and carbon dioxide as raw materials. In addition, provided are the prepared cyclic carbonate, and an electrolyte including the same: 
     
       
         
         
             
             
         
       
         
         
           
             in Chemical Formula 1, R 1  is hydrogen, (C1-C20)alkyl or halogen; R 2  is hydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen or nitro.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2015-0132290, filed on Sep. 18, 2015, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The following disclosure relates to a catalyst for preparing cycliccarbonate, particularly, a catalyst used for selectively preparingcyclic carbonate by reacting an alkylene oxide compound with carbondioxide, and a method for preparing cyclic carbonate using the same. Inaddition, the present invention relates to the prepared cycliccarbonate, and an electrolyte including the same.

BACKGROUND

The conversion of abundant and renewable C₁ source and carbon dioxide(CO₂) to commodity chemicals has received a lot of recent attention inpart as a sustainable solution for carbon dioxide recycling andreduction. Particularly, reaction of carbon dioxide and epoxides to formpolycarbonates or cyclic carbonate is considered as one of the promisingindustrial processes.

The cyclic carbonate is used as raw materials of polycarbonate,intermediates for cosmetics and pharmaceutical process, oxyalkylationagents in a dye synthesis process, protective agents of a processequipment, and solvents of a fiber production process. In addition, thecyclic carbonate may be used as an intermediate in preparing alkyleneglycol from alkylene oxide. Recently, a range at which the cycliccarbonate is used has been continuously expanded to a solvent of apolymer electrolyte of a secondary battery, etc.

Several catalytic systems such as transition metal complexes ororganocatalysts were reported to promote the reaction of carbon dioxideand alkylene oxide. As a well-known example, there are salen-basedcomplexes (salen=N,N′-bis(salicylidiene)ethylenediamine) of Al, Cr, Mn,Co and Zn that are recognized to be effective for both polycarbonate andcyclic carbonate synthesis. [Cr(salen)] and [Co(salen)] complexes forpolycarbonate synthesis were developed; meanwhile, binuclear[Al(salen)]₂O complex for selective cyclic carbonate synthesis wasdeveloped.

In addition to metal-dependent selectivity, research into ligandmodification in a complex to improve reactivity and selectivity of acatalyst was conducted, and a highly active carbon dioxide/propyleneoxide copolymerization catalyst prepared by incorporating co-catalystammonium salts in [Co(salen)] complexes has been reported, which isbeing developed for industrial production of polypropylene carbonate.

In addition, it has been reported that mononuclear Al complexes anddinuclear Fe complexes based on amino tris(phenolate) ligands haveexcellent reactivity and selectivity in the cyclic carbonate synthesis.

As other different methods, for example, Japanese Patent Laid-OpenPublication No. S56-128778 discloses cyclic carbonate prepared in acatalyst system consisting of an alkali metal compound and a crowncompound, Japanese Patent Laid-Open Publication No. S59-13776 usedquaternary ammonium and alcohol, WO 2005/003113 used tetraalkylphosphonium halide, and Korean Patent Laid-Open Publication No.2005-0115694 used a catalyst system consisting of a metal salt and analiphatic cyclic amine salt. However, these synthesis methods haveproblems in that since a reaction yield is low under mild reactionconditions, high temperature and a long period of reaction time arerequired to increase yield, and moisture contents of raw materials,i.e., carbon dioxide and alkylene oxide should be controlled to behundreds of ppm or less.

U.S. Pat. No. 5,283,356 discloses a phthalocyanine catalyst includingCo, Cr, Fe, Mn, Ni, Ti, V, Zr, etc., and Japanese Patent Laid-OpenPublication No. H7-206547 discloses a catalyst substituted with rubidium(Rb) or cesium (Cs) ions instead of hydrogen ions of hetero polyacid,respectively. However, these catalysts are high cost, wherein a reactiontemperature is high as 120° C. to 180° C., and a yield is low as 30 to90%.

As described above, the catalyst used for industrial synthesis of thecyclic carbonate according to the related art has problems in thatreaction conditions are complicated, for example, a reaction temperatureshould be high, a moisture content of raw materials should besignificantly low, etc., and selectivity and yield are low, and areaction time is long.

RELATED ART DOCUMENT Patent Documents

-   (Patent Document 1) Japanese Patent Laid-Open Publication No.    S56-128778-   (Patent Document 2) Japanese Patent Laid-Open Publication No.    S59-13776-   (Patent Document 3) WO 2005/003113-   (Patent Document 4) Korean Patent Laid-Open Publication No.    2005-0115694-   (Patent Document 5) U.S. Pat. No. 5,283,356.-   (Patent Document 6) Japanese Patent Laid-Open Publication No.    H7-206547

Non-Patent Documents

-   (Non-Patent Document 1) Darensbourg, D. J.; Yarbrough, J. C. J. Am.    Chem. Soc. 2002, 124, 6335-6342.-   (Non-Patent Document 2) Qin, Z.; Thomas, C. M.; Lee, S.;    Coates, G. W. Angew. Chem. Int. Ed. 2003, 42, 5484-5487.-   (Non-Patent Document 3) North, M.; Pasquale, R. Angew. Chem. Int.    Ed. 2009, 48, 2946-2948.-   (Non-Patent Document 4) Whiteoak, C. J.; Kielland, N.; Laserna, V.;    Escudero-Adán E. C.; Martin, E.; Kleij, A. W. J. Am. Chem. Soc.    2013, 135, 1228-1231.-   (Non-Patent Document 5) Whiteoak, C. J.; Gjoka, B.; Martin, E.;    Belmonte, M. M.; Escudero-Adán E. C.; Zonta, C.; Licini, G.;    Kleij, A. W. Inorg. Chem. 2012, 51, 10639-10649.

SUMMARY

The present inventors found that selectivity for preparing cycliccarbonate through a reaction of alkylene oxide and carbon dioxide couldbe increased by a pre-organized rigid metal complex so as to have acis-binding site available for reducing an activation barrier of thereaction, and completed the present disclosure.

An embodiment of the present invention is directed to providing a metalcatalyst capable of selectively preparing cyclic carbonate by reactingalkylene oxide with carbon dioxide.

Another embodiment of the present invention is directed to providing amethod for selectively preparing cyclic carbonate in a high yield byreacting alkylene oxide with carbon dioxide using the metal catalyst.

In addition, still another embodiment of the present invention isdirected to providing the prepared cyclic carbonate, and an electrolyteincluding the same.

In one general aspect, a catalyst used for selectively preparing cycliccarbonate by reacting an alkylene oxide compound with carbon dioxide,and a method for preparing cyclic carbonate using the same.

Hereinafter, the present invention will be described in detail.

Here, unless technical and scientific terms used herein are definedotherwise, they have meanings generally understood by those skilled inthe art to which the present invention pertains. In addition, repeateddescriptions for technical constitution and function as the same as therelated art will be omitted.

The present invention provides a catalyst for selectively preparingcyclic carbonate from alkylene oxide and carbon dioxide, and thecatalyst of the present invention is a metal complex including a ligandrepresented by Chemical Formula 1 below and a trivalent metal in Group 8or Group 13:

in Chemical Formula 1, R¹ is hydrogen, (C1-C20)alkyl or halogen; R² ishydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen or nitro.

The ligand represented by Chemical Formula 1 of the present inventionhas three phenolate donors bonded to a trisubstituted carbon and asalicylidene moiety.

The ligand represented by Chemical Formula 1 may be selected from thefollowing structures, but is not limited thereto:

The ligand represented by Chemical Formula 1 is effectively preparedthrough an imidization reaction of dihydroxybenzophenone and ammonia, areductive amination reaction, and a reaction with salicylaldehydederivative.

More specifically, the ligand represented by Chemical Formula 1 isprepared by the following steps as shown in Reaction Scheme 1 below:

1) preparing an imine compound represented by Chemical Formula B byreacting dihydroxybenzophenone represented by Chemical Formula A withammonia;

2) preparing a secondary amine compound represented by Chemical FormulaC below by reducing the imine compound represented by Chemical FormulaB; and

3) preparing the ligand represented by Chemical Formula 1 by reactingthe secondary amine compound represented by Chemical Formula C with asalicylaldehyde derivative represented by Chemical Formula D:

in Reaction Scheme 1, R¹ is hydrogen, (C1-C20)alkyl or halogen; R² ishydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen or nitro.

The imine compound represented by Chemical Formula B is prepared byreacting commercially available 2,2′-dihydroxybenzophenone representedby Chemical Formula A with ammonia. In general, it is significantlyunstable to separate the imine compound formed from ammonia; however,the imine compound represented by Chemical Formula B may be separateddue to internal hydrogen bonds present between an imine group and twophenol groups. The ammonia is used in an excessive amount relative tothe 2,2′-dihydroxybenzophenone represented by Chemical Formula A, and ispreferably used in an amount of 2 to 10 equivalents relative to 1equivalent of the 2,2′-dihydroxybenzophenone represented by ChemicalFormula A. The ammonia is preferably saturated aqueous ammonia. Theimidization reaction is possible to be performed at a general reactiontemperature, and preferably, may be performed at 20° C. to 40° C.

The preparation of the imine compound represented by Chemical Formula Bmay be performed under an organic solvent or by a neat reaction, whereinthe organic solvent is not limited as long as it is capable ofdissolving the reaction materials. The neat reaction is to perform theimidization reaction by mixing the dihydroxybenzophenone represented byChemical Formula A with ammonia without using the organic solvent. Asolvent for the reaction is preferably an inert solvent selected fromthe group consisting of methanol, ethanol, isopropanol, butanol,acetone, ethyl acetate, acetonitrile, isopropyl ether, methyl ethylketone, methylene chloride, dichlorobenzene, chlorobenzene,dichloroethane, tetrahydrofuran, toluene, benzene, xylene, mesitylene,dimethyl formamide, dimethyl sulfoxide, etc., in consideration ofsolubility of reaction materials and easiness of removal thereof, andmore preferably, methanol, ethanol, or mixed solvents thereof.

The prepared imine compound represented by Chemical Formula B may beused for next reaction without further separation or purification, ormay be subjected to purification if needed.

The prepared imine compound represented by Chemical Formula B is reducedby using a reducing agent to thereby prepare the secondary aminecompound represented by Chemical Formula C. The reducing agent may bemetal hydride, preferably, at least one selected from the groupconsisting of NaBH₄, NaBH (OAc)₃, NaBH₂ (OAc)₂, NaBH₃OAc, NaBH₃CN, KBH₄,KBH (OAc), LiAlH₄, B₂H₆ and DIBAL-H (diisobutylaluminium hydride), andmore preferably, NaBH₄. The reducing agent is not limited in view of anamount, but is used in the same amount or an excess amount relative tothe imine compound represented by Chemical Formula B. Preferably, thereducing agent is used at 1 to 5 equivalents relative to 1 equivalent ofthe imine compound represented by Chemical Formula B. The reductionreaction is possible to be performed at a general reaction temperature,and preferably, may be performed at 20° C. to 40° C.

The preparation of the secondary amine compound represented by ChemicalFormula C may be performed under an organic solvent, wherein the organicsolvent is not limited as long as it is capable of dissolving thereaction materials. A solvent for the reaction is preferably an inertsolvent selected from the group consisting of methanol, ethanol,isopropanol, acetone, ethyl acetate, acetonitrile, isopropyl ether,methyl ethyl ketone, methylene chloride, dichlorobenzene, chlorobenzene,dichloroethane, tetrahydrofuran, toluene, benzene, and xylene inconsideration of solubility of reaction materials and easiness ofremoval thereof, and more preferably, methanol, ethanol, or mixedsolvents thereof.

The ligand represented by Chemical Formula 1 is prepared by reacting thesecondary amine compound represented by Chemical Formula C with thesalicylaldehyde derivative represented by Chemical Formula D. Thesalicylaldehyde derivative represented by Chemical Formula D is used inthe same amount or an excess amount relative to the secondary aminecompound represented by Chemical Formula C. Preferably, thesalicylaldehyde derivative is used at 1 to 5 equivalent relative to 1equivalent of the secondary amine compound represented by ChemicalFormula C. In addition, in order to improve the reaction yield, thereaction may be performed by further including a base, wherein the basemay be a tertiary organic amine. An example of the tertiary organicamine may be aliphatic amine represented by R′R″R′″N (wherein R′, R″ andR′″ are each independently (C1-C6)alkyl, (C2-C16)alkenyl, (C6-C12)arylor benzyl). Specifically, examples of the tertiary organic amine mayinclude trimethylamine, triethylamine, tripropylamine,dimethylethylamine, tributylamine, diisopropyl ethylamine, andtriphenylamine, and preferably, trimethylamine or triethylamine. It ispreferable that the reaction may be performed at 20° C. to 40° C.

The preparation of the ligand represented by Chemical Formula 1 may beperformed under an organic solvent, wherein the organic solvent is notlimited as long as it is capable of dissolving the reaction materials. Asolvent for the reaction may be methanol, ethanol, isopropanol, acetone,ethyl acetate, acetonitrile, isopropyl ether, methyl ethyl ketone,methylene chloride, dichlorobenzene, chlorobenzene, dichloroethane,tetrahydrofuran, toluene, benzene, xylene, etc.

All reactions are completed after confirmation through TLC, etc.,whether starting materials are completely consumed. When the reaction iscompleted, the solvent may be distilled under reduced pressure, and atarget material may be separated and purified by general methods such asfiltration, column chromatography, recrystallization, etc.

More specifically, the catalyst for selectively preparing the cycliccarbonate according to the present invention is represented by ChemicalFormula 2 below:

in Chemical Formula 2, M is Fe or Al; R¹ is hydrogen, (C1-C20)alkyl orhalogen; and R² is hydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen ornitro.

The metal complex represented by Chemical Formula 2 according to thepresent invention includes a ligand consisting of a planar salicylidenegroup as well as a trisubstituted carbon center possessing apre-organized bite angle ideal to accommodate a 6-coordinate metalcenter as illustrated in FIG. 1. Meanwhile, an amino tris(phenolate)ligand included in the catalyst for selectively preparing the cycliccarbonate according to the related art has three flexible methylenegroups, and therefore, the enhanced rigidity effect of the ligandskeleton itself according to the present invention may not be observedin the related art.

More specifically, the metal complex represented by Chemical Formula 2above according to an exemplary embodiment of the present invention maybe selected from the following structures, but the present invention isnot limited thereto:

The catalyst for selectively preparing the cyclic carbonate according tothe present invention may be prepared by reacting the ligand compoundrepresented by Chemical Formula 1 and a trivalent metal halide in Group8 or Group 13.

In addition, the present invention provides a method for preparingcyclic carbonate by reacting carbon dioxide with alkylene oxide usingthe metal complex represented by Chemical Formula 2 as a catalyst,wherein the alkylene oxide which is a reaction material includes atleast one epoxide in the chemical structure, and in the reaction withcarbon dioxide, all epoxides react with carbon dioxide to form thecyclic carbonate.

More specifically, the present invention provides a method for preparingcyclic carbonate represented by Chemical Formula 4 below by reactingcarbon dioxide with alkylene oxide represented by Chemical Formula 3below, using the metal complex represented by Chemical Formula 2 aboveas a catalyst:

in Chemical Formulas 2, 3 and 4,

M is Fe or Al;

R¹ is hydrogen, (C1-C20)alkyl or halogen;

R² is hydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen or nitro;

R^(1a) and R^(4a) are each independently hydrogen, (C1-C10)alkyl,halo(C1-C10)alkyl or (C6-C12)aryl, and R^(1a) and R^(4a) may be linkedvia (C3-C5)alkylene with or without a fused ring to form a ring, whereinthe formed ring may be further substituted with vinyl,—(CH₂)_(a)SiR¹¹R¹²R¹³, oxiranyl or(7-oxa-bicyclo[4.1.0]heptane-3-yl)acetyl;

R^(3b) and R^(4b) are each independently hydrogen, (C1-C10)alkyl,halo(C1-C10)alkyl or (C6-C12)aryl, and R^(3b) and R^(4b) may be linkedvia (C3-C5)alkylene with or without a fused ring to form a ring, whereinCH₂ of the alkylene may be substituted with O, and the formed ring maybe further substituted with vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³,1,3-dioxolan-2-one-4-yl or(hexahydrobenzo[d][1,3]dioxol-2-one-5-yl)acetyl;

R¹¹ to R¹³ are each independently (C1-C10)alkyl or (C1-C10)alkoxy; and

a is an integer of 1 to 5.

The term “alkyl” used herein means monovalent linear or branchedsaturated hydrocarbon radical only consisting of carbon atoms andhydrogen atoms, and examples of the alkyl radical include methyl, ethyl,propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl,dodecyl, etc., but the present invention is not limited thereto.

The term “haloalkyl” used herein means alkylradical substituted withhalogen atom as defined above, and examples of the haloalkyl includefluoromethyl, difluoromethyl, trifluoromethyl, fluoroethyl,difluoroethyl, bromopropyl, etc., but the present invention is notlimited thereto.

The term “aryl” used herein is an organic radical derived from aromatichydrocarbon due to removal of one hydrogen, and includes a single ringsystem or a fused ring system including 4 to 7 ring atoms, preferably, 5or 6 ring atoms in each ring, and even includes a form in which aplurality of aryls are connected by a single bond. Specific examples ofaryl include phenyl, naphthyl, biphenyl, anthryl, indenyl, fluorenyl,etc., but the present invention is not limited thereto.

The term “alkoxy” used herein means —O-alkyl radical, wherein the‘alkyl’ is the same as described above. Examples of the alkoxy radicalinclude methoxy, ethoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, etc.,but the present invention is not limited thereto.

In the method for preparing cyclic carbonate according to an exemplaryembodiment of the present invention, the alkylene oxide represented byChemical Formula 3 is more preferably an epoxide derivative fused with5-membered to 7-membered ring, and specifically, may be selected fromthe following structures, but the present invention is not limitedthereto:

R¹¹ is hydrogen, vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³, oxiranyl or((7-oxa-bicyclo[4.1.0]heptane-3-yl)acetyl).

In the method for preparing cyclic carbonate according to an exemplaryembodiment of the present invention, the metal complex represented byChemical Formula 2 is preferably used in an amount of 0.1 to 2.0 mol %relative to the alkylene oxide represented by Chemical Formula 3,wherein when the used amount of the metal complex is less than 0.1 mol%, a reaction speed is excessively decreased, and when the used amountthereof is more than 2.0 mol %, the reaction speed and the selectivityare not improved any more, such that economical efficiency in using thecatalyst is deteriorated.

In the method for preparing cyclic carbonate according to an exemplaryembodiment of the present invention, an ammonium co-catalyst or anamine-based co-catalyst may be further included for an improved reactionspeed and high yield, wherein the ammonium co-catalyst or theamine-based co-catalyst is preferably used in an amount of 0.1 to 10.0mol % relative to the alkylene oxide represented by Chemical Formula 3.The ammonium co-catalyst may be aliphatic amine salts, aromatic aminesalts, or heteroaromatic amine salts, and specifically, may be selectedfrom the group consisting of tetrabutylammonium bromide (NBu₄Br),tetramethylammonium bromide (NMe₄Br), tetraethylammoniumtetrafluoroborate (NEt₄BF₄), tetrapropylammonium bromide (NPr₄Br),tetrahexylammonium chloride (N[(CH₂)₅CH₃]₄Cl), tetrapentylammoniumbromide (N[(CH₂)₄CH₃]₄Br), tetraheptylammonium bromide(N[(CH₂)₆CH₃]₄Br), tetraoctylammonium bromide (N[CH₂)₇CH₃]₄Br),trimethyldodecylammonium chloride (CH₃(CH₂)₁₁N(CH₃)₃Cl),trimethyltetradecylammonium bromide (CH₃(CH₂)₁₃N(CH₃)₃Br),trimethylhexadecylammonium chloride (CH₃(CH₂)₁₅N(CH₃)₃Cl),methyltrioctylammonium chloride (CH₃N[(CH₂)₇CH₃]₃Cl), tetrabutylammoniumfluoride (NBu₄F), tetrabutylammonium chloride (NBu₄Cl),tetrabutylammonium iodide (NBu₄I), 1-butyl-3-methylimidazolium bromide([bmim]Br), 1-butyl-3-methylimidazolium chloride ([bmim]Cl), andbis(triphenylphosphine)iminium chloride ([((C₆H₅)₃P)₂N]Cl, PPNCl), andthe amine-based co-catalyst may be specifically selected from the groupconsisting of triethylamine (Et₃N), 1,8-diazabicycloundec-7-ene (DBU),pyridine (C₅H₅N), and 4-dimethylaminopyridine (C₇H₁₀N₂, DMAP), and theco-catalyst is preferably tetrabutylammonium bromide (NBu₄Br).

Even though carbon dioxide and the alkylene oxide contain nitrogen,hydrogen, carbon monoxide, a low concentration of hydrocarbon, or water,they do not significantly affect on the reaction. Industrially producedcarbon dioxide and alkylene oxide are usable without furtherpurification.

In the method for preparing cyclic carbonate according to an exemplaryembodiment of the present invention, the reaction temperature ispreferably 25□ to 120□. When the reaction temperature is excessivelylow, the reaction speed is decreased. When the reaction temperature isexcessively high, alkylene oxide which is the raw material degraded, orself-polymerization occurs, which deteriorates selectivity of the cycliccarbonate. In addition, in the reaction, carbon dioxide is supplied in areactor under a pressure of 1 bar to 10 bar. When a reaction pressure isless than 1 bar, the reaction speed is remarkably decreased, and whenthe reaction pressure is more than 10 bar, there is no improvementeffect with the reaction speed, which is not economical.

In the method for preparing cyclic carbonate according to an exemplaryembodiment of the present invention, the reaction may be performed underan organic solvent or by a neat reaction. The neat reaction is to reactcarbon dioxide with alkylene carbonate without using the organicsolvent. In some cases, an organic solvent is usable to prevent rapidheat generation. The organic solvent to be usable may be any solventthat is generally used in the art. For example, the organic solvent maybe methylene chloride, chloroform, ethyl acetate, tert-methylbutylether,toluene, isopropylalcohol, dioxane, acetonitrile, alkylene carbonate,etc., but the present invention is not limited thereto.

Further, the present invention relates to the prepared cyclic carbonateand an electrolyte including the same, wherein the cyclic carbonate isrepresented by Chemical Formula 4 below:

in Chemical Formula 4, R^(3b) and R^(4b) are each independentlyhydrogen, (C1-C10)alkyl, halo(C1-C10)alkyl or (C6-C12)aryl, and R^(3b)and R^(4b) may be linked via (C3-C5)alkylene with or without a fusedring to form a ring, wherein the formed ring may be further substitutedwith vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³, 1,3-dioxolan-2-one-4-yl or(hexahydrobenzo[d][1,3]dioxol-2-one-5-yl)acetyl;

R¹¹ to R¹³ are each independently (C1-C10)alkyl or (C1-C10)alkoxy; and

a is an integer of 1 to 5.

The cyclic carbonate represented by Chemical Formula 4 according to anexemplary embodiment of the present invention may be represented byChemical Formula 5 or 6 below:

in Chemical Formulas 5 and 6,

L¹ and L² are each independently O or (C1-C3)alkylene, and the alkylenemay be further substituted with vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³,1,3-dioxolan-2-one-4-yl or(hexahydrobenzo[d][1,3]dioxol-2-one-5-yl)acetyl;

R¹¹ to R¹³ are each independently (C1-C10)alkyl or (C1-C10)alkoxy; and

a is an integer of 1 to 5.

The cyclic carbonate according to an exemplary embodiment of the presentinvention may be selected from the following structures, but the presentinvention is not limited thereto:

The cyclic carbonate represented by Chemical Formula 4 above accordingto the present invention may be used as a solvent or an additiveconstituting an electrolyte in a lithium secondary battery to exhibitmore stable and excellent electrolyte performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates Reaction Scheme for preparing cyclic carbonate usinga catalyst according to the present invention.

FIG. 2 illustrates a crystalline structure of a metal complex[Fe-1a.THF]₂ of Example 1.

FIG. 3 illustrates a crystalline structure of a metal complex [Fe-1b]₂of Example 2.

FIG. 4 illustrates a crystalline structure of a metal complex [Al-1a]₂of Example 9.

FIG. 5 illustrates a crystalline structure of a metal complex Al-1b.THFof Example 10.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a configuration of the present invention will be describedin detail with reference to Examples. These Examples are provided onlyfor assisting in the entire understanding of the present invention, andit will be obvious to those skilled in the art that the scope of thepresent invention is not construed to be limited to these examples.

Commercially available reagents and carbon dioxide (99.99%) were usedwithout further purification or drying. All reactions were performed ina 80 mL stainless steel reactor. ¹H NMR (400 MHz) and ¹³C NMR (100 MHz)analyses were recorded on a Bruker Advance III HD spectrometer. The massspectra were analyzed on a High Resolution Hybrid Tandem LC-MS/MSspectrometer.

[Preparation Examples 1 to 8] Preparation of Ligands 1a to 1h

Preparation of Compound B

To a stirred solution of 2,2′-dihydroxybenzophenone (Compound A, DHBP)(30 g, 140 mmol) in MeOH (300 mL), 4 equivalents of saturated ammonia(38 mL, 560 mmol) was added at ambient temperature, followed by stirringfor 16 hours. As the reaction proceeded, since it was difficult to stir,methanol (300 mL) was additionally added during the stirring. Theformation of Compound B was confirmed by ¹H NMR (in DMSO-d₆). When thereaction was completed, yellow precipitate was filtered and washed withmethanol to obtain Compound B as a yellow solid (26.7 g, 90% yield).

¹H NMR (400 MHz, DMSO-d₆): δ 7.33-7.29 (m, 2H), 7.06-7.05 (d, 2H),6.90-6.88 (d, 2H), 6.76-6.72 (br, 2H); ¹³C NMR (100 MHz, DMSO-d₆): δ177.3, 132.4, 130.0, 117.8, 117.1; HRMS (ESI) m/z calculated forC₁₃H₁₂NO₂ [H⁺]: 214.0868, found: 214.0867.

Preparation of Compound C

To a stirred mixture of the Compound B (20 g, 94 mmol) in methanol (200mL), NaBH₄ (6.4 g, 170 mmol, 1.8 equiv.) was added at ambienttemperature, followed by stirring for 1 hour. Then, saturated HClaqueous solution (24.3 ml, 28 mmol, 3 equiv.) was slowly added at 0° C.,followed by stirring for 30 minutes. Solvent was evaporated thoroughlyand the product was redissolved in ethanol. White solid (Na salt) wasprecipitated and removed with filtration. The ethanol solution wasconcentrated and CHCl₃ was added to obtain a white solid. The whitesolid product was filtered to obtain Compound C (21.6 g, 91% yield).

¹H NMR (400 MHz, DMSO-d₆): δ 10.32 (s, 2H), 8.65 (s, 3H), 7.32-7.29 (dd,2H), 7.19-7.15 (m, 2H), 7.07-7.05 (dd, 2H), 6.83-6.79 (t, 2H), 5.87-5.86(d, 1H); ¹³C NMR (100 MHz, DMSO-d₆): δ 155.0, 129.4, 128.4, 123.4,118.8, 115.7, 47.4; HRMS (ESI) m/z calculated for C₁₃H₁₄NO₂ [H⁺]:216.1019, found: 216.1002.

Preparation of Compound 1a

To a methanol solution of the Compound C (4 g, 15.9 mmol), triethylamine(2.3 ml, 16.7 mmol, 1.05 equiv.) and salicylaldehyde (16.7 mmol, 1.05equiv.) were added and stirred. The degree of reaction was monitoredusing ¹H NMR, and after 1 hour of the stirring, a prepared yellow solidwas filtered and washed with methanol to obtain a compound 1a (84%yield).

Preparation Example 1: Compound 1a

¹H NMR (400 MHz, DMSO-d₆): δ 13.90 (s, 1H), 9.56 (s, 2H), 8.65 (s, 1H),7.47-7.44 (dd, 1H), 7.34-7.30 (m, 1H), 7.14-7.08 (m, 4H), 6.89-6.84 (m,4H), 6.82-6.78 (td, 2H); ¹³C NMR (100 MHz, DMSO-d₆): δ 164.8, 160.8,154.8, 132.4, 131.8, 128.2, 128.1, 127.8, 118.8, 118.8, 118.5, 116.5,115.3, 63.7; HRMS (ESI) m/z calculated for C₂₀H₁₈NO₃ [H]⁺: 320.1287,found: 320.1271.

Preparation of Compound 1b

Compound 1b (yellow solid, 87% yield) was obtained by performing thesame method as the preparation method of Compound 1a except for using5-nitrosalicylaldehyde (16.7 mmol, 1.05 equiv.) instead of usingsalicylaldehyde.

Preparation Example 2: Compound 1b

¹H NMR (400 MHz, DMSO-d₆): δ 15.15 (s, 1H), 10.02 (s, 2H), 8.94 (s, 1H),8.51-8.50 (d, 1H), 8.07-8.04 (dd, 1H), 7.20-7.10 (td, 2H), 7.13-7.10(dd, 2H), 6.89-6.87 (dd, 2H), 6.84-6.80 (td, 2H), 6.65-6.53 (d, 1H),6.33 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆): δ 176.6, 165.9, 155.0, 134.5,132.2, 129.2, 128.5, 124.5, 122.2, 119.1, 115.6, 114.0, 62.0; HRMS (ESI)m/z calculated for C₂₀H₁₇N₂O₅ [H⁺]: 365.1137, found: 365.1109.

Preparation of Compound 1c

To a methanol solution of the Compound C (4 g, 15.9 mmol), triethylamine(2.3 ml, 16.7 mmol, 1.05 equiv.) and 3,5-dichlorosalicylaldehyde (16.7mmol, 1.05 equiv.) were added and stirred. The degree of reaction wasmonitored using ¹H NMR, and after 1 hour of the stirring, solvent wasconcentrated by evaporation, followed by recrystallization usingchloroform to obtain Compound 1c (Yellow solid, 66% yield).

Preparation Example 3: Compound 1c

¹H NMR (400 MHz, DMSO-d₆): δ 15.34 (s, 1H), 9.87 (s, 2H), 7.58-7.57 (d,1H), 7.51-7.50 (d, 1H), 7.17-7.11 (m, 4H), 6.87-6.85 (dd, 2H), 7.13-7.10(dd, 2H), 6.83-6.79 (td, 2H), 6.31 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆):δ 164.4, 162.9, 154.9, 132.8, 130.5, 128.8, 128.4, 125.6, 124.3, 119.0,117.5, 117.1, 115.5, 62.1; HRMS (ESI) m/z calculated for C₂₀H₁₆N₁O₃Cl₂[H⁺]: 388.0507, found: 388.0461.

Preparation of Compound 1d

Compound 1d (yellow solid, 59% yield) was obtained by performing thesame method as the preparation method of Compound 1a except for using5-fluorosalicylaldehyde (16.7 mmol, 1.05 equiv.) instead of usingsalicylaldehyde.

Preparation Example 4: Compound 1d

¹H NMR (400 MHz, DMSO-d₆): δ 13.58 (s, 1H), 9.57 (s, 2H), 8.63 (s, 1H),7.42-7.38 (dd, 1H), 7.22-7.15 (td, 1H), 7.12-7.07 (m, 4H), 6.90-6.76 (m,5H), 6.28 (s, 1H).

Preparation of Compound 1e

To a methanol solution of the Compound C (350 mg, 1.39 mmol, 1.0equiv.), triethylamine (0.19 mL, 1.39 mmol, 1.0 equiv.) and5-methoxysalicylaldehyde (1.39 mmol, 1.0 equiv) were added and stirred.The degree of reaction was monitored using ¹H NMR, and after 6 hours ofthe stirring, solvent was evaporated, and the obtained mixture wasdissolved in ethyl acetate, and washed with water. The ethyl acetatesolution was dried over magnesium sulfide, and solvent was evaporated,followed by recrystallization using chloroform and hexane to obtainCompound 1e (yellow solid, 88% yield).

Preparation Example 5: Compound 1e

¹H NMR (400 MHz, DMSO-d₆): δ 13.19 (s, 1H), 9.51 (s, 2H), 8.59 (s, 1H),7.11-7.07 (m, 5H), 6.96-6.92 (dd, 1H), 6.82-6.75 (m, 5H), 6.28 (s, 1H),3.70 (s, 3H).

Preparation of Compound 1f

Compound 1f (yellow solid, 73% yield) was obtained by performing thesame method as the preparation method of Compound 1c except for using5-methylsalicylaldehyde (16.7 mmol, 1.05 equiv.) instead of using3,5-dichlorosalicylaldehyde.

Preparation Example 6: Compound 1f

¹H NMR (400 MHz, DMSO-d₆): δ 13.50 (s, 1H), 9.56 (s, 2H), 8.55 (s, 1H),7.24 (s, 1H), 7.15-7.06 (m, 5H), 6.84-6.75 (m, 5H), 6.27 (s, 1H), 2.22(s, 3H).

Preparation of Compound 1g

To a methanol solution of the Compound C (350 mg, 1.39 mmol, 1.0equiv.), triethylamine (0.19 mL, 1.39 mmol, 1.0 equiv.) and3,5-di-t-butylsalicylaldehyde (1.39 mmol, 1.0 equiv) were added andstirred. The degree of reaction was monitored using ¹H NMR, and after 6hours of the stirring, solvent was evaporated, and the obtained mixturewas dissolved in ethyl acetate, and washed with water. The ethyl acetatewas dried over magnesium sulfide, and evaporated to obtain Compound 1g(yellow solid, 89% yield).

Preparation Example 7: Compound 1g

¹H NMR (400 MHz, DMSO-d₆): δ 14.45 (s, 1H), 9.44 (s, 2H), 8.65 (s, 1H),7.32-7.28 (dd, 2H), 7.15-7.08 (m, 4H), 6.87-6.85 (dd, 2H), 6.82-6.78(td, 2H), 6.36 (s, 1H), 1.39 (s, 9H), 1.32 (s, 9H); ¹³C NMR (100 MHz,DMSO-d₆): δ 166.1, 157.8, 154.8, 139.6, 135.6, 128.2, 128.0, 128.0,126.5, 126.1, 118.8, 117.9, 115.3, 63.4, 34.6, 33.8, 31.3, 29.3; HRMS(ESI) m/z calculated for C₂₈H₃₄N₁O₃ [H⁺]: 432.2539, found: 432.2553.

Preparation of Compound 1h

Compound 1h (yellow solid, 73% yield) was obtained by performing thesame method as the preparation method of Compound 1e except for using3-t-butyl-5-nitrosalicylaldehyde (1.39 mmol, 1.0 equiv) instead of using5-methoxysalicylaldehyde.

Preparation Example 8: Compound 1h

¹H NMR (400 MHz, DMSO-d₆): δ 15.14 (s, 1H), 10.07 (s, 2H), 8.92-8.89 (d,1H), 8.40-8.39 (d, 1H), 7.94-7.93 (d, 1H), 7.21-7.17 (td, 2H), 7.13-7.11(dd, 2H), 6.91-6.89 (dd, 2H), 6.86-6.82 (td, 2H), 6.32-6.31 (d, 1H),1.34 (s, 9H); ¹³C NMR (100 MHz, DMSO-d₆): δ 177.7, 166.6, 155.0, 141.9,133.2, 131.3, 129.4, 128.6, 124.5, 124.2, 119.1, 115.6, 113.5, 61.8,34.8, 28.7; HRMS (ESI) m/z calculated for C₂₄H₂₅N₂O₅ [H⁺]: 421.1763,found: 421.1758.

[Examples 1 to 10] Preparation of Metal Complex

[Example 1] Preparation of Metal Complex Fe-1a

To a methanol mixture of the Compound 1a (300 mg, 0.94 mmol), FeCl₃ (152mg, 0.94 mmol, 1 equiv.) and triethylamine (285 mg, 2.82 mmol, 3 equiv.)were added and stirred for 12 hours. After the stirring was completed, aprepared brown solid was filtered and washed with methanol to obtain ametal complex Fe-1a (72% yield).

UV-Vis [THF, nm (L mol⁻¹ cm⁻¹)]: ˜260 (sh, 40000), ˜342 (sh, 10000), 423(7000). IR (KBr pellet, cm⁻¹): 3465, 3064, 3045, 2996, 2894, 1627, 1616,1546, 1481, 1479, 1401, 1295, 1151, 1114, 1037, 887, 823, 755; HRMS(ESI) m/z calculated for [{C₂₀H₁₄FeN₁O₃}₂+Na]⁺: 767.05, found: 766.87;Anal. calculated for C₄₀H₂₈Fe₂N₂O₆.2EtOH: C, 63.18; H, 4.82; N, 3.35.Found: C, 63.18; H, 5.05; N, 3.21. Crystal required for structuralanalysis through X-ray diffraction was obtained by slowly diffusingdiethyl ether in saturated tetrahydrofuran (THF) solution of Fe-1a (FIG.2).

[Example 2] Preparation of Metal Complex Fe-1b

A metal complex Fe-1b (85% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1b instead of using the Compound 1a.

UV-Vis [THF, nm (L mol⁻¹ cm⁻¹)]: 276 (30000), 346 (30000), ˜460 (sh,6000). IR (KBr pellet, cm⁻¹): 3471, 3075, 3006, 2902, 1637, 1610, 1587,1482, 1473, 1394, 1319, 1101, 1035, 954, 894, 846, 755; HRMS (ESI) m/zcalculated for [{C₂₀H₁₃FeN₂O₅}₂+Na]⁺: 857.02, found: 856.80; Anal.Calculated for C₄₀H₂₆Fe₂N₄O₁₀.2EtOH: C, 57.04; H, 4.13; N, 6.05. Found:C, 57.21; H, 4.27; N, 5.81. Crystal required for structural analysisthrough X-ray diffraction was obtained by slowly evaporating saturatedbenzene (THF) solution of Fe-1b (FIG. 3).

[Example 3] Preparation of Metal Complex Fe-1c

A metal complex Fe-1c (85% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1c instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3641, 3429, 3057, 3010, 2970, 2925, 2891, 1626,1560, 1528, 1483, 1477, 1441, 1416, 1388, 1302, 1290, 1267, 1242, 1223,1180, 1117, 1105, 1066, 1034, 970, 937, 889, 863, 802, 794, 775, 755.

[Example 4] Preparation of Metal Complex Fe-1d

A metal complex Fe-1d (98% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1d instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3627, 3419, 3057, 3012, 2891, 1691, 1626, 1595,1552, 1477, 1466, 1450, 1387, 1290, 1267, 1254, 1225, 1188, 1147, 1117,1066, 1034, 985, 968, 937, 895, 860, 822, 756.

[Example 5] Preparation of Metal Complex Fe-1e

A metal complex Fe-1e (77% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1e instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3430, 3055, 3006, 2935, 2900, 2835, 1626, 1610,1547, 1477, 1450, 1388, 1348, 1290, 1267, 1196, 1161, 1112, 1071, 1031,895, 823, 756.

[Example 6] Preparation of Metal Complex Fe-1f

A metal complex Fe-1f (94% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1f instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3415, 3055, 3012, 2920, 2866, 1624, 1595, 1545,1477, 1450, 1385, 1292, 1267, 1238, 1227, 1165, 1138, 1115, 1070, 1036,893, 856, 825, 814, 754.

[Example 7] Preparation of Metal Complex Fe-1g

A metal complex Fe-1g (93% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1g instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3060, 3002, 2958, 2904, 2870, 1622, 1597, 1558,1539, 1477, 1450, 1412, 1388, 1361, 1301, 1255, 1219, 1173, 1116, 1070,1036, 1011, 930, 916, 887, 847, 820, 800, 791, 752.

[Example 8] Preparation of Metal Complex Fe-1h

A metal complex Fe-1h (82% yield) was obtained by performing the samemethod as the preparation of the metal complex Fe-1a except for usingthe Compound 1h instead of using the Compound 1a.

IR (KBr pellet, cm⁻¹): 3417, 3062, 3006, 2958, 2908, 2870, 1633, 1595,1566, 1502, 1481, 1450, 1442, 1419, 1392, 1311, 1288, 1267, 1244, 1200,1180, 1153, 1117, 1068, 1036, 985, 926, 889, 845, 820, 800, 754.

[Example 9] Preparation of Metal Complex Al-1a

To a tetrahydrofuran solution of Compound 1a (300 mg, 0.94 mmol), 2.0 MAlMe₃ heptane solution (0.47 ml, 0.94 mmol, 1 equiv.) was added andstirred for 3 hours. After the stirring was completed, solvent wasevaporated to be concentrated, and hexane was added to obtain a whitesolid. The white solid was filtered to obtain Al-1a (62% yield).

¹H NMR (400 MHz, DMSO-d₆): δ 8.67 (s, 1H), 7.38 (m, 2H), 7.22 (d, 2H),6.96 (t, 2H), 6.83 (d, 1H), 6.78 (t, 1H), 6.58 (m, 4H), 5.67 (s, 1H);¹³C NMR (100 MHz, DMSO-d₆): δ 164.5, 163.4, 158.4, 134.8, 133.3, 130.1,128.3, 127.7, 120.9, 120.1, 119.7, 117.1, 116.4, 76.3; UV-Vis [THF, nm(L mol⁻¹ cm⁻¹)]: 265 (33000), 273 (30000), 294 (13000), 337 (10000); IR(KBr pellet, cm⁻¹): 3056, 3029, 3008, 2969, 2923, 2886, 1633, 1606,1554, 1482, 1457, 1405, 1311, 1294, 1274, 1240, 1214, 1186, 1151, 1132,1116, 1076, 1035, 906, 894, 860, 835, 817, 794, 755; HRMS (ESI) m/zcalculated for [{C₄₀H₂₈N₂O₆}+Na]⁺: 709.15, found: 709.15. Anal.Calculated for C₄₀H₂₈Al₂N₂O₆: C, 69.97; H, 4.11; N, 4.08. Found: C,69.42; H, 4.26; N, 3.94. Crystal required for structural analysisthrough X-ray diffraction was obtained by slowly diffusing diethyl etherin saturated tetrahydrofuran (THF) solution of Al-1a (FIG. 4).

[Example 10] Preparation of Metal Complex Al-1b

A metal complex Al-1b (70% yield) was obtained by performing the samemethod as the preparation of the metal complex Al-1a except for usingthe Compound 1b instead of using the Compound 1a.

¹H NMR (400 MHz, DMSO-d₆): δ 8.66 (s, 1H), 8.39 (s, 1H), 8.09 (dd, 1H),7.07 (dd, 2H), 6.89 (td, 2H), 6.69 (d, 1H), 6.46 (dd, 2H), 6.41 (td,2H), 5.46 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆): δ 171.6, 162.5, 160.2,135.3, 130.4, 130.1, 128.8, 128.0, 127.4, 121.7, 119.6, 119.5, 114.4,77.9, 67.0, 25.1; UV-Vis [THF, nm (L mol⁻¹ cm⁻¹)]: ˜249 (sh, 22000), 262(19000), ˜278 (sh, 15000), 294 (13000), 325 (16000). IR (KBr pellet,cm⁻¹): 3060, 2989, 2981, 2910, 1650, 1602, 1565, 1488, 1394, 1336, 1303,1209, 1130, 1101, 1045, 1035, 1014, 954, 904, 833, 800, 754, 692, 626;HRMS (ESI) m/z calculated for C₂₀H₁₄AlN₂O₅ [H]⁺: 389.07, found: 389.07;Anal. Calculated for C₂₀H₁₃AlN₂O₅: C, 62.61; H, 4.60; N, 6.08. Found: C,62.62; H, 4.69; N, 5.92. Crystal required for structural analysisthrough X-ray diffraction was obtained by slowly diffusing pentane insaturated tetrahydrofuran (THF) solution of Al-1a (FIG. 5).

[Example 11] Preparation of Cyclic Carbonate Using Carbon Dioxide andCyclohexene Oxide

To a 80 mL stainless steel reactor, 0.5 mol % catalyst, 2.5 mol %tetrabutylammonium bromide (NBu₄Br), and 1 ml of cyclohexene oxide werecharged. The reactor was charged and discharged with 5 bar of CO₂ twiceand finally charged with 10 bar of CO₂. The reactor was sealed, followedby stirring at 100° C. to perform the reaction. After the reaction wascompleted, an aliquot of the reaction mixture was dissolved in CDCl₃ andanalyzed by ¹H NMR.

Each catalyst, reaction time, and yield and selectivity of the productswere shown in Table 1 below.

TABLE 1 Reaction Time Yield Selectivity Entry Catalyst (h) (%) (I:II) 1Fe-1a 2 45 >50:1  2 Fe-1a 8 83 23:1 3 Fe-1b 8 80 49:1 4 Fe-1c 8 89 20:15 Fe-1d 8 91  9:1 6 Fe-1e 8 75  8:1 7 Fe-1f 8 71 23:1 8 Fe-1g 8 87  2:19 Fe-1h 8 84  5:1 10 Al-1a 8 92 1.1:1  11 Al-1b 8 89 1.8:1 

It was observed from entry 1 and entry 2 that when the same catalyst wasused, as the reaction time passes, the conversion rate was increased,and selectivity was slightly decreased, from which could be appreciatedthat a large amount of cyclic carbonate was present in the obtainedproduct.

In entry 3, the most excellent selectivity was exhibited in the samereaction time.

It could be confirmed that entry 10 and entry 11 using aluminum metalcomplex had similar reactivity to the case of using iron metal complex;however, slightly decreased selectivity.

Therefore, it could be appreciated that when the metal complex of thepresent invention including the ligand including three phenolate donorsbonded to the trisubstituted carbon and the salicylidene moiety is usedas the catalyst for the reaction of carbon dioxide and alkylene oxide,the cyclic carbonate could be selectively prepared with high conversionrate to alkylene oxide.

[Example 12] Preparation of Cyclic Carbonate

Epoxide compounds 3-4 and 3-8 were prepared according to the methodreported in document (Laserna, V.; Fiorani, G.; Whiteoak, C. J.; Martin,E.; Escudero-Adán, E.; Kleij, A. W. Angew. Chem., Int. Ed. 2014, 53,10416).

The cyclic carbonation was performed as follows.

As shown in Table 2 below, the catalyst of the present invention, NBu₄Brand 1 g or 1 ml of epoxide were charged in 80 mL stainless steelreactor. Fe-1b of Example 2 was used as the catalyst, and NBu₄Br wasused as the co-catalyst. The reactor was charged and discharged with 5bar of CO₂ twice and finally charged with 10 bar of CO₂. The reactor wassealed, followed by stirring at 100° C. for predetermined time. Afterthe reaction was completed, an aliquot of the reaction mixture wasanalyzed by ¹H NMR spectroscopy using CDCl₃ as the solvent. The crudemixture was passed through the silica using 10:1 mixture of chloroformand ethyl acetate as an eluent to remove catalyst and ammonium salt.Solvent was removed under vacuum and target cyclic carbonate wasobtained.

All of prepared cyclic carbonates 1-1 to 1-10 were cis-selective and theNMR spectra thereof were the same as the previously reported NMR spectra(Cyclic carbonates 1-1 to 1-3, 1-5, 1-6 to 1-10: Laserna, V.; Fiorani,G.; Whiteoak, C. J.; Martin, E.; Escudero-Adán, E.; Kleij, A. W. Angew.Chem., Int. Ed. 2014, 53, 10416; Cyclic carbonate 1-4: Orsini, F.;Sello, G.; Bestetti, G. Tetrahedron: Asymmetry 2001, 12, 2961.).

TABLE 2 Co- Catalyst catalyst Re- used used action Epoxide amount amounttime Entry compound (mol %) (mol %) (h) 1

0.2 5.0 12 3-1 2

0.2 5.0 18 3-2 3

0.2 5.0 18 3-3 4

0.2 5.0 12 3-4 5

0.2 5.0 12 3-5 6

0.4 10.0 12 3-6 7

0.1 1.5 12 3-7 8

0.1 1.5 12 3-8 9

0.5 5.0 12 3-9 10

2.0 10.0 12  3-10

1) Compound 1-1:

Conversion rate 99%, Amount 1.25 g (91% Yield); ¹H NMR (400 MHz, CDCl₃):δ 4.67-4.62 (m, 2H), 1.89-1.76 (m, 4H), 1.59-1.49 (m, 2H), 1.41-1.32 (m,2H); ¹³C NMR (100 MHz, CDCl₃): 155.37, 75.75, 26.64, 19.04.

2) Compound 1-2:

Conversion rate 99%, Amount 1.14 g (90% Yield), mixture of diastereomers[see Angew. Chem., Int. Ed. 2014, 53, 10416.]; ¹H NMR (400 MHz, CDCl₃):δ 5.76-5.66 (m, 2H), 5.05-4.96 (m, 4H), 4.78-4.60 (m, 4H), 2.34-2.09 (m,5H), 2.03-1.94 (m, 1H), 1.82-1.51 (m, 5H), 1.38-1.27 (m, 2H), 1.21-1.11(m, 1H); ¹³C NMR (100 MHz, CDCl₃): δ 155.19, 155.16, 140.95, 114.26,113.96, 76.02, 75.66, 75.65, 75.15, 36.34, 33.89, 33.55, 31.67, 26.68,25.79, 25.70, 25.06.

3) Compound 1-3:

Conversion rate 99%, Amount 0.94 g (77% Yield), mixture of diastereomers[see Angew. Chem., Int. Ed. 2014, 53, 10416.]; ¹H NMR (400 MHz, CDCl₃):δ 4.76-4.73 (quint, 1H), 4.69-4.66 (quint, 1H), 4.65-4.58 (m, 2H),3.53-3.51 (m, 18H), 2.30-2.04 (m, 4H), 1.80-1.76 (m, 1H), 1.70-1.47 (m,4H), 1.41-1.07 (m, 8H), 0.97-0.87 (m, 1H), 0.63-0.58 (m, 4H); ¹³C NMR(100 MHz, CDCl₃): δ 155.31, 155.27, 76.45, 76.08, 76.07, 75.59, 50.64,35.30, 33.97, 32.41, 32.10, 29.12, 28.84, 26.88, 26.03, 25.64, 25.05,6.37, 6.25.

4) Compound 1-4:

Conversion rate 99%, Amount 1.42 g (94% Yield); ¹H NMR (400 MHz, CDCl₃):δ 7.41-7.39 (dd, 1H), 7.36-7.28 (m, 2H), 7.21-7.19 (dd, 1H), 5.70-5.68(d, 1H), 5.20-5.16 (quint, 1H), 3.00-2.92 (m, 1H), 2.72-2.66 (dt, 1H),2.33-2.26 (m, 1H), 2.02-1.94 (m, 1H); ¹³C NMR (100 MHz, CDCl₃): δ154.85, 138.30, 130.96, 129.93, 129.53, 128.84, 127.48, 75.78, 75.53,27.27, 23.87.

5) Compound 1-5:

Conversion rate 99%, Amount 1.86 g (>99% Yield), mixture ofdiastereomers [see Angew. Chem., Int. Ed. 2014, 53, 10416.]; ¹H NMR (400MHz, CDCl₃): δ 4.92-4.69 (m, 2H), 4.63-4.16 (m, 3H), 2.44-2.35 (m, 1H),2.21-1.86 (m, 2H), 1.82-1.69 (m, 2H), 1.67-1.24 (m, 2H); ¹³C NMR (100MHz, CDCl₃): δ 154.75, 154.73, 154.67, 154.62, 154.58, 79.35, 79.14,79.04, 79.02, 75.40, 75.23, 75.14, 75.04, 74.70, 74.64, 74.62, 67.61,67.54, 67.37, 36.49, 36.36, 33.24, 33.09, 28.78, 28.45, 27.60, 26.39,25.72, 25.10, 24.96, 21.00, 20.44, 19.64, 19.18.

6) Compound 1-6:

Conversion rate 99%, Amount 1.68 g (>99% Yield), mixture ofdiastereomers; ¹H NMR (400 MHz, CDCl₃): δ 4.91-4.81 (m, 2H), 4.76-4.66(m, 6H), 4.08-3.91 (m, 4H), 2.75-2.68 (m, 1H), 2.43-2.23 (m, 6H),2.16-1.95 (m, 7H), 1.91-1.71 (m, 7H), 1.71-1.57 (4H), 1.49-1.07 (m, 3H);¹³C NMR (100 MHz, CDCl₃): δ 174.02, 173.98, 173.21, 173.19, 154.93,154.90, 154.77, 154.74, 154.72, 75.60, 75.55, 75.52, 75.19, 75.13,74.99, 74.95, 74.75, 74.62, 68.20, 68.17, 68.06, 37.43, 37.41, 37.34,37.24, 35.62, 32.17, 30.57, 30.51, 30.47, 29.43, 29.35, 29.32, 29.27,29.25, 28.77, 28.74, 28.00, 26.17, 26.13, 25.42, 25.37, 25.34, 25.20,25.17, 25.16, 25.12, 25.09, 22.37, 21.92, 21.87, 21.85, 21.44, 21.40;HRMS (ESI) m/z calculated for C₁₆H₂₀O₈ [M+Na⁺]: 363.1056, found:363.1075.

7) Compound 1-7:

Conversion rate 99%, Amount 1.36 g (95% Yield); ¹H NMR (400 MHz, CDCl₃):δ 5.07-5.06 (m, 2H), 2.11-2.04 (m, 2H), 1.81-1.58 (m, 4H); ¹³C NMR (100MHz, CDCl³): δ 155.51, 81.92, 33.08, 21.53.

8) Compound 1-8:

Conversion rate 99%, Amount 1.40 g (94% Yield); ¹H NMR (400 MHz, CDCl₃):δ 7.52-7.50 (dt, 1H), 7.44-7.40 (td, 1H), 7.37-7.31 (m, 2H), 6.01-5.99(d, 1H), 5.46-5.42 (m, 1H), 3.40-3.39 (m, 1H); ¹³C NMR (100 MHz, CDCl₃):δ 154.84, 140.18, 136.58, 131.20, 128.37, 126.63, 125.74, 83.71, 79.89,38.16.

9) Compound 1-9:

Conversion rate 99%, Amount 1.65 g (98% Yield); ¹H NMR (400 MHz, CDCl₃):δ 5.20-5.19 (m, 2H), 4.24-4.21 (dd, 2H), 3.57-3.53 (m, 2H); ¹³C NMR (100MHz, CDCl₃): δ 154.53, 80.18, 73.07.

10) Compound 1-10:

Conversion rate 99%, Amount 0.98 g (84% Yield). 0.9 ml of substrate wasused. ¹H NMR (400 MHz, CDCl₃): δ 4.84-4.78 (m, 2H), 1.99-1.86 (m, 4H),7.84-1.74 (m 2H), 1.66-1.57 (m, 1H), 1.52-1.42 (m, 1H), 1.35-1.25 (m,2H); ¹³C NMR (100 MHz, CDCl₃): δ 154.74, 79.91, 30.23, 30.00, 23.58.

The metal complex according to the present invention is a metal complexhaving a novel structure and consisting of a ligand having threephenolate donors bonded to a trisubstituted carbon and a salicylidenemoiety, and a trivalent metal in Group 8 or Group 13, which has apre-organized bite angle ideal to accommodate a 6-coordinate metalcenter, such that an enhanced rigidity effect of a ligand skeletonitself of the present invention is exhibited.

Therefore, the method for preparing cyclic carbonate from the reactionof alkylene oxide and carbon dioxide using the metal complex accordingto the present invention may increase selectivity by the pre-organizedrigid metal complex so as to have the cis-binding site available forreducing the activation barrier of the reaction, thereby highlyselectively preparing the cyclic carbonate with 90% or more of completeconversion rate to alkylene oxide.

Further, the cyclic carbonate according to the present invention may beused as a solvent or an additive constituting an electrolyte in alithium secondary battery to exhibit more stable and excellentelectrolyte performance.

What is claimed is:
 1. A metal complex comprising a ligand representedby Chemical Formula 1 below and a trivalent metal in Group 8 or Group13:

in Chemical Formula 1, R¹ is hydrogen, (C1-C20)alkyl or halogen; R² ishydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen or nitro.
 2. The metalcomplex of claim 1, wherein the metal complex is represented by ChemicalFormula 2 below:

in Chemical Formula 2, M is Fe or Al; R¹ is hydrogen, (C1-C20)alkyl orhalogen; R² is hydrogen, (C1-C20)alkyl, (C1-C20)alkoxy, halogen ornitro.
 3. The metal complex of claim 2, wherein the metal complex isselected from the following structures:


4. A method for preparing cyclic carbonate by reacting carbon dioxidewith alkylene oxide using the metal complex of claim 1, as a catalyst.5. The method of claim 4, wherein the alkylene oxide is represented byChemical Formula 3 below, and the cyclic carbonate is represented byChemical Formula 4 below:

in Chemical Formulas 3 and 4, R^(3a) and R^(4a) are each independentlyhydrogen, (C1-C10)alkyl, halo(C1-C10)alkyl or (C6-C12)aryl, and R^(3a)and R^(4a) may be linked via (C3-C5)alkylene with or without a fusedring to form a ring, wherein the formed ring may be further substitutedwith vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³, oxiranyl or(7-oxa-bicyclo[4.1.0]heptane-3-yl)acetyl; R^(3b) and R^(4b) are eachindependently hydrogen, (C1-C10)alkyl, halo(C1-C10)alkyl or(C6-C12)aryl, and R^(3b) and R^(4b) may be linked via (C3-C5)alkylenewith or without a fused ring to form a ring, wherein the formed ring maybe further substituted with vinyl, —(CH₂)_(a)SiR¹¹R¹²R¹³,1,3-dioxolan-2-one-4-yl or(hexahydrobenzo[d][1,3]dioxol-2-one-5-yl)acetyl; R¹¹ to R¹³ are eachindependently (C1-C10)alkyl or (C1-C10)alkoxy; and a is an integer of 1to
 5. 6. The method of claim 4, wherein the metal complex catalyst hasan amount of 0.1 to 2.0 mol % relative to the alkylene oxide.
 7. Themethod of claim 4, wherein an ammonium co-catalyst or an amine-basedco-catalyst is further included.
 8. The method of claim 7, wherein theammonium co-catalyst or the amine-based co-catalyst has an amount of 0.1to 10.0 mol % relative to the alkylene oxide.
 9. The method of claim 8,wherein the ammonium co-catalyst is selected from the group consistingof tetrabutylammonium bromide (NBu₄Br), tetramethylammonium bromide(NMe₄Br), tetraethylammonium tetrafluoroborate (NEt₄BF₄),tetrapropylammonium bromide (NPr₄Br), tetrahexylammonium chloride(N[(CH₂)₅CH₃]₄Cl), tetrapentylammonium bromide (N[(CH₂)₄CH₃]₄Br),tetraheptylammonium bromide (N[(CH₂)₆CH₃]₄Br), tetraoctylammoniumbromide (N[CH₂)₇CH₃]₄Br), trimethyldodecylammonium chloride(CH₃(CH₂)₁₁N(CH₃)₃Cl), trimethyltetradecylammonium bromide(CH₃(CH₂)₁₃N(CH₃)₃Br), trimethylhexadecylammonium chloride(CH₃(CH₂)₁₅N(CH₃)₃Cl), methyltrioctylammonium chloride(CH₃N[(CH₂)₇CH₃]₃Cl), tetrabutylammonium fluoride (NBu₄F),tetrabutylammonium chloride (NBu₄Cl), tetrabutylammonium iodide (NBu₄I),1-butyl-3-methylimidazolium bromide ([bmim]Br),1-butyl-3-methylimidazolium chloride ([bmim]Cl), andbis(triphenylphosphine)iminium chloride ([((C₆H₅)₃P)₂N]Cl, PPNCl), andthe amine-based co-catalyst is selected from the group consisting oftriethylamine (Et₃N), 1,8-diazabicycloundec-7-ene (DBU), pyridine(C₅H₅N), and 4-dimethylaminopyridine (C₇H₁₀N₂, DMAP).
 10. The method ofclaim 4, wherein a reaction temperature is 25 to 120° C., and a reactionpressure is 1 to 10 bar.
 11. The method of claim 4, wherein the reactionis a neat reaction.